Validating across bounded contexts in Domain Driven Design (DDD)?

I have a project with two bounded contexts; game and sidegame.

In some cases I need to do validation across both bounded contexts. For example, if a player wants to play a sidegame then it must be validated they are playing the "main" game also.

In DDD what patterns can be used to achieve this? So far I have considered:

1. Event driven messaging between the contexts, but this feels weird as I end up with aggregates in partial states (i.e. waiting for a player to be validated).


2. Shared data, where ONYL ONE bounded context can read. I'm not sure if this is a DDD anti-pattern?


3. That perhaps my bounded contexts shouldn't be separate. However, I want to avoid creating a single massive domain context.

Any advice would be appreciated.